def is_prime(n):
    if n<2:
        return False
    for i in range(2,int(n**0.5)+1):
        if n % i == 0:
            return False
    return True

print(is_prime(13))

#递归阶乘
def factorial(n):
    if n==1:
        return 1
    else:
        return n*factorial(n-1)
